VOLXJMETEIC EELATIONS OE OZONE. 
117 
the spark or silent discharge. When this operation was finished, the vessel was replaced 
in the calorimeter, the siphon tubes were opened, and the levels of the acid in the two 
vessels again read. 
In order to examine the effects of heat, the reservoir of the vessel was placed in a sort 
of air-bath, formed by suspending a long copper cylinder above a Leslie’s gas-burner, 
the siphon tube being outside the cylinder, fig. 6. In this way a temperature of 300° C., 
which was sufiScient to destroy in a short time all the ozone reactions, was readily 
obtained. This temperature was estimated without difficulty, by observing the amount 
of compression of the air in the outer leg of the siphon tube. Our apparatus, with a 
slight modification, might, in fact, be employed as a thermometer for all temperatures 
below that at which glass begins to soften. 
It will probably tend to perspicuity, if we state, before going further, some of the 
general results of our experiments on the action of the electrical discharge on pure 
oxygen. 
I. When the silent discharge is passed through pure and dry oxygen^ a contraction takes 
place. This contraction proceeds, at first rapidly, hut afterwards more slowly, till it 
attains a limit, which, in one of our experiments, amounted to f^th of the original volume 
of the gas. 
II. If a few electrical sparks he passed through the gas in this contracted state, it 
expands till it recovers about threefourths of the contraction; hut, however long the sparks 
are passed, the gas never recovers its original volume. 
III. When electrical sparks are passed through pure and dry oxygen, it contracts, hut 
to a much smaller extent than when acted on hy the silent discharge. The oxygen is, in 
fact, brought to the same volume as when electrical sparks are passed through the same gas, 
previously contracted hy the silent discharge. 
IV. When oxygen, contracted either by the silent discharge or hy sparks, is exposed for 
a short time to the temperature q/’270° C., it is restored to its original volume, and, on 
opening the vessel, the ozone reactions are found to have disappeared. 
The following experiments, taken from a large number which gave similar results, 
mil serve to illustrate the foregoing statements. 
a. In a vessel, whose reservoir had a capacity of 5 cub. cent., sparks were passed for 
ten minutes, and produced a contraction of 5'9 millims., as measured by the change of 
levels of the acid in the siphon tube. By heating the vessel afterwards to 300° C., the 
levels were restored to within OT millim. of their original position. 
With the silent discharge in the same vessel, a contraction of 39-5 millims. (corre- 
sponding to about one-thirtieth of the volume of the gas) was obtained in ten minutes. 
Of this contraction heat restored 38-7 millims. This slight difference of 0-8 millim. is 
probably due to distortion of the vessel produced by heat. 
Again, the silent discharge gave in ten minutes a contraction of 37' 6 millims., of which 
sparks, subsequently passed for seven minutes, destroyed 29*7 millims., leaving 7'9 millims. 
undestroyed. 
MDCCCLX. 
R 
